✍ Scribed by Elena López-Torres; Jonathan R. Dilworth
No coin nor oath required. For personal study only.
Careful metal selection: Control of the reaction conditions of Cu^II^ and Sn^IV^ with Me~2~NNHCSNHPh permits the selective synthesis of metal complexes or a range of heterocyclic compounds generated by the oxidative coupling of two thiosemicarbazides (see figure).magnified image
The reactions of 1,1‐dimethyl‐4‐phenylthiosemicarbazide (LH) with Cu^II^ and Sn^IV^ have been investigated. If THF or methanol is used as solvent with Cu^II^, oxidative cyclisation and coupling are observed, yielding a 1,2,4‐thiadiazole or a 1,3,4‐thiadiazolium salt. SnI~4~ is also able to induce oxidative coupling of two thiosemicarbazide ligands, yielding 1,2,4‐thiadiazolium or 1,2,4‐triazolium salts, with I~3~^−^ as the counterion, depending on the reaction conditions. By contrast, reaction of LH with SnI~4~ in acetone yields a 1,3‐thiazolium salt, with I^−^ as counterion. Reaction with Cu^II^ salts or SnI~4~ in basic media leads to the formation of metal complexes containing two deprotonated thiosemicarbazide ligands. In the reaction of CuCl~2~ in water in the presence of acid a complex containing two neutral ligands is obtained. Reactions with SnCl~4~ are not able to induce ligand cyclisation, although a coordination compound with two neutral ligands was isolated from methanol.
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